LABOUR must end the trade unions' "abuse and inappropriate" influence over its leadership selection process, Peter Mandelson has said as he savaged the party's election approach.

The former minister and Hartlepool MP also called for an end to the party's "unhealthy" dependence on trade union funding.

Lord Mandelson said the unions have an important role to play in society and politics but added: "I am not happy with a Labour Party so clearly dependent on people who pay the piper and then in many cases can call the tune.

"That's not a good look, that's not right for a Labour Party appealing for votes in the 21st century."

The Labour peer, appearing on BBC One's the Andrew Marr Show, earlier said around 2.5 million "political levy-paying trade unionists" are being invited to declare themselves as Labour supporters and could have a vote in the leadership contest, which is based on a one member, one vote system.

He said: "What I say to that is if we're going to have people declaring that they're Labour supporters in that way and given a vote then every single one of those individuals needs to be validated by the party staff and party headquarters.

"We cannot open ourselves up to the sort of abuse and inappropriate influence that the trade unions weighed in with in our leadership election in 2010."

Lord Mandelson accused "trade union machines" of offering unrivalled backing to Ed Miliband in 2010 in an attempt to influence members - and said this "sort of abuse" should be guarded against this time around.

Asked if it was time for Labour to break the link with trade unions, Lord Mandelson said: "It's undoubtedly unhealthy for us to be so dependent on trade union funding."

Lord Mandelson said Mr Miliband had delivered a "passionate and professional" approach during the General Election campaign.

But he said in 2010 the party was sent out on a "giant political experiment" to "wave our fists angrily at the nasty Tories and wait for the public to realise how much they had missed us".

He went on: "Well they weren't missing us and they didn't miss us. Instead they ripped the sort of stripes off our shoulders and that really is the depth of our defeat and the scale of the challenge we face now.

"I was there in the 1980s and early 1990s as the party's campaign director. I think now the scale of the challenge we face and the need for rethinking and remodernisation of the party is akin to the sort of scale of challenge we faced in the late 1980s. That's how serious it is."

Asked if that was a terrible legacy for Mr Miliband's leadership, Lord Mandelson said: "It's a measure of how far we have to go and what we have to do in order to climb back, and far from embarking on a sort of short-term beauty contest of leaders what we really need is a very, very thorough debate in the party of the sort that was denied us in 2010."

Lord Mandelson said the party had ignored people who aspired to improve their lives and also backed Labour's desire to ensure social justice and fairness.

He questioned why this group should vote for Labour if the party was not totally committed to helping them.

He said: "Literally we were sent out and told to say things and to make an argument, if you can call it an argument, which basically said we're for the poor, we hate the rich, ignoring completely the vast swathe of the population who exist in between."

On Mr Miliband's predators versus producers speech, Lord Mandelson added: "I thought it was a completely useless label that led nowhere in any serious debate both about the partnership we need to have with business, but also how business needs to change."

He said there is a need for a more reformed and responsible capitalism, adding people in business realised they need to "live for the long-term not the short-term financial interests".

Lord Mandelson also said the party should have recognised not every pound of public spending by the previous Labour administration was "wholly wise or wholly justified or whatever".

He added: "But don't make any mistake about this. Labour overspending did not cause the banking crisis."

On whether he had an advisory role during the election, Lord Mandelson told Pienaar's Politics on BBC Radio 5 Live: "The first time I was rung up was actually the day before polling day and asked for my view on how I thought we could get Ed into government if he was a close second."

Addressing what was missing from Labour's election offer, he said: "There was a great hole in the middle of the Polo mint and it's called the economy".

Pressed to be more specific about what should have been included, Lord Mandelson replied: "An economic policy."

He added there was nothing in the manifesto about economic growth, productivity, new technologies and the scale of the challenges for the country.